Friends and relatives will be able to travel to hospital with critically injured patients in a new helicopter being tested by a charity.
The new Eurocopter 135 is larger and faster than the Thames Valley Air Ambulance Trust's previous aircraft.
This will give paramedics more room to treat casualties on board as well as carry relatives to hospital.
It will cost the trust up to £1.2m a year if they decide to continue permanently with the new helicopter.
The trust was launched in June 1999 and flies more than 1,000 emergency missions each year, making it one of the busiest air ambulances in the country, the trust says.
The air ambulance is based at White Waltham and can reach Slough and Windsor in three minutes, Reading in four, Newbury and Oxford in nine, and Milton Keynes in twelve minutes.
"The new helicopter will be on loan at some point later this year," said Colin Lee, chair of Thames Valley Air Ambulance Trust.